The present invention relates to a machine for the aseptic treatment of containers in bottling plant.
In plants for bottling and packaging containers for drinks (e.g. bottles) under aseptic conditions, to prevent contamination the container treatment area (for instance in the sterilizer, rinsing machine, filling machine, capping machine) must be duly isolated from the exterior environment and maintained sterile.
According to a first constructive solution, the various machines of the plant (e.g. sterilizer, rinsing machine, filling machine, capping machine) are totally inserted inside voluminous aseptic chambers kept in overpressure conditions relative to the exterior environment by using fans to inject air filtered by absolute filters, which then has a unidirectional outward flow in correspondence with the openings required for the entry/exit of the containers into/from the chambers in which the machines and the components of the plant are inserted. In this way, the possible entrance of micro-organisms into the container treatment area is prevented.
However, since the dimensions of the machines, which are generally rotary, are considerable, the dimensions of the aseptic chambers are so large as to make it difficult to manage them and to maintain sterile conditions.
According to another solution, to reduce the size of the chambers, only the process areas of the machines are isolated, leaving the remaining part of the machines in an uncontrolled atmosphere.
In rotary machines, the process area to be isolated is defined between a rotating part and a fixed part, and a barrier is required between the rotating part, in which the process organs are mounted (for instance the sterilizing nozzles of a sterilizer, or the filling valves of a filling machine, or the closing heads of a capping machine, . . . ) and the fixed walls, such as the protective casing towards the exterior of the machine or towards the transmission organs.
For this purpose, gaskets made of elastomeric material have been used, generally applied to the rotating part, which slide on the normally metallic fixed part.
Considering that the main conditions of reliability of the solution (smooth, hard sliding surface with low friction coefficient and parallel to the gasket; low sliding speeds) contrast with the considerable dimensions of the machines that prevent, due to the required work process tolerances and production rates, the achievement of these conditions, it is readily apparent that the main drawbacks of this solution are due to the rapid wear of the gasket with consequent loss of seal.
Another known solution provides for the use of labyrinth seals, which overcome the gasket wear problems because they do not imply any physical contact between the parts in relative motion.
However, the quality of the seal depends on the distance between the moving parts: as said distance decreases, seal quality increases, but achieving reduced distances (i.e. tens of millimeters) is particularly complex and costly in such large machines because the tolerances of the mechanical work processes are such as to make it difficult to attain such small distances.
With this solution, moreover, another possible path for the exchange of air with the exterior environment is given by the labyrinth seals and therefore, to obtain an adequate overpressure a greater flow rate of sterile air is necessary, with higher costs and with the danger of a lack of isolation.